Rail track support

ABSTRACT

A prestressed concrete rail track support which is made up of a plurality of prestressed concrete sections which are individually post-tensioned by means of bonded stressing tendons. When the strips are laid gaps are left between them so that the tendons may be tensioned. The ends of the stressing tendons are left extending into the gaps which are subsequently filled with concrete and the extending portions separately tensioned. On to the concrete a rail or rails are laid each being securely affixed to the concrete, the strength of the structure is assured by bonding the stressing tendons to the concrete in such a manner that the crack pattern spacing of the structure at ultimate load is less than approximately 15 inches.

United States Patent Crimp et al.

[ 1 Aug. 29, 1972 [54] RAIL TRACK SUPPORT 221 Filed: Sept. 15, 1970 21 Appl. No.: 72,284

[52] US. Cl ..238/25, 238/91 [51 Int. Cl. ..E0lb 3/38 [58] Field of Search ..238/24, 25, 26, 91, 92, I15,

[56] References Cited UNITED STATES PATENTS 2,750,] 18 6/1956 Hastings et a1. ..238/25 934,054 9/1909 Eisig ..238l25 3,300,140 1/1967 Moses et a1 ..238/25 1,820,911 9/1931 Henderson ..238/25 1,063,087 5/1931 Valkelberg ..238/26 Primary Examiner-Gerald M. Forlenza Assistant ExaminerRichard A. Bertsch ArtomeyMichael S. Striker ABSTRACT A prestressed concrete rail track support which is made up of a plurality of prestressed concrete sections which are individually post-tensioned by means of bonded stressing tendons. When the strips are laid gaps are left between them so that the tendons may be tensioned. The ends of the stressing tendons are let! extending into the gaps which are subsequently filled with concrete and the extending portions separately tensioned. On to the concrete a rail or rails are laid each being securely affixed to the concrete, the strength of the structure is assured by bonding the stressing tendons to the concrete in such a manner that the crack pattern spacing of the structure at ultimate load is less than approximately 15 inches.

7 Claims, 3 Drawing Figures RAIL TRACK SUPPORT BACKGROUND OF THE INVENTION a. Field of the Invention The present invitation relates to a rail track support and has for its object the provision of a rail track support constructed from prestressed concrete.

Description of the Prior Art The traditional form of rail track support as used on railways involves the use of timber sleepers set in ballast. The present invention provides a form of rail track principally continuously supported in a longitudinal direction, and in particular taking advantage of the internal arching action of confined prestressed concrete the track having a number of advantages among which are the avoidance of the necessity for using ballast which is costly, a reduction in the amount of work in preparing the base and the possession of greater overload characteristics. In addition, constructions according to the present invention are well adapted for use where very heavy rolling loads are involved, for example with gantries.

If use were made of conventional methods of analysis of stressed concrete structures it would appear extremely difficult if not impossible to construct a satisfactory rail track support in reinforced concrete, as such methods of analysis would tend to show that a prohibitive amount of concrete and reinforcing steel would be required. The present invention rests on the discovery that conventional methods of analysis give very erroneous results when applied to structures in which very good bonding is achieved between the stressing tendons and the concrete through which they pass. Experimental work has led to the discovery of a new form of analysis of such structures involving the concept of an internal arching action which shows that a very high load carrying capacity of the rail track for varying soil strength may be achieved, provided that there is a high degree of bond between the stressing tendons, and thus a low ultimate load crack width spacmg.

SUMMARY OF THE INVENTION The invention consists in a rail track support made up of a plurality of prestressed concrete sections each section consisting of a longitudinally extending strip of concrete, post tensioned by means of bonded stressing tendons, the strips being laid with gaps between them, to permit tensioning of the tendons, the stressing tendons extending from the ends of the strips into the gaps, the gaps being filled with concrete and the extending portions being separately tensioned, a rail or rails being laid on the base so formed, each rail being securely affixed to the base, the bonding of the stressing tendons to the concrete of the strips being such that the crack pattern spacing of the structure at ultimate load is less than approximately fifteen inches.

The invention further consists in the method of constructing a rail track support as defined above.

Preferred Embodiment of the Invention In order that the invention may be better understood and put into practice a preferred form thereof is hereinafter described by way of example with reference to the accompanying drawings in which:

0 precision.

A strip of concrete 1] is then laid by means of a slip form machine onto polythene sheets 12. The width of the strip will depend on the requirements of the track to be laid; in the present case a width of 4 feet is used for the support of a single rail 13, the thickness of the concrete being 8 inches. The length of the strip in this particular case is three hundred feet.

The strip is laid in a conventional manner by machine and during laying the necessary steel reinforcing 14, and stressing tendons 15 are incorporated in the strip, the latter being enclosed in suitable ducting 16 which is correctly positioned by the action of the machine as concrete is extruded from it. As the strip is laid two spiral steel members 17 consisting of a spiral of 4 inches in diameter of one-quarter inch steel rod and 2 inch pitch, are pushed into the upper surface of the concrete, spaced equally 6 inches on either side of the centerline of the strip. These are set into the concrete so that they are half submerged in it, the projecting half being subsequently embedded in the second stage concrete 18 described below and serving to unite it with the strip.

After the 300 -foot strip has been laid and allowed to set, it is post-tensioned in a conventional manner, the stressing tendons 15 being grouted into the ducting l6 and anchored at each end of the strip 11 by anchoring means 21 and being allowed to project beyond it for a distance of about three feet. Longitudinal unstressed steel reinforcing members 22 are also left extending from the end of the strip, to provide additional reinforcement in the gap.

After completion of the laying of the strip a 4 -foot gap is left and a second 300 -foot strip 11' is laid in the same manner as the first and this is shown on the right hand side of FIGS. 2 and 3. It will be appreciated that stressing tendons 15 and 15' from the end of each strip project in opposite directions into the four foot gap between them as well as the longitudinal reinforcing members 22 and 22', the latter being laid side by side to provide reinforcement through the gap.

The ends of the stressing tendons l5 and 15' are taped and passed through holes in a W section steel joining member 23 which extends transversely across the gap in the middle thereof. The holes are in the central sloping portions of the joining member 23 and in order to pass through them the ends of the stressing tendons are led upwardly at an angle of about 45as seen in FIG. 3. The stressing tendons 15 and 15' are thus joined end to end to provide a continuous stressed reinforcement throughout the length of the rail track support.

After covering the projecting ends of the tendons l5 and 15' to prevent adherence to the concrete, the four foot gap is filled with concrete, except for the interior of the W section member 23, and this is allowed to set. The projecting portion of the tendons l5 and 15' are then stressed and anchored to the joining member 23 by wedges 23 and their ends cut off flush so as not to project above the surface of the strip.

The interior of the W section member 23 is then filled with concrete to the level of the original three hundred foot strips so as to form a continuous upper surface.

A 94 lb steel rail 13 is then laid along the centerline of the strips 11 and 11' with a steel packing under it at foot centers. A strip of second stage concrete 18 20 inches wide is then laid so as to embed the bottom flange and part of the web of the rail 13 and the upper halves of the steel spirals 17.

In order to obtain the necessary load bearing characteristics for the rail track it is essential to ensure that there is a high degree of bonding between the stressing tendons and the concrete by the use of suitable stressing tendons and suitable grout in the conduits for the tendons. The crack pattern spacing of the structure at ultimate load should be less than approximately 15 inches.

A rail track support constructed as described above has been found very effective in use and economical to lay.

The embodiment of the invention described above is given merely to illustrate the application of the invention and details of construction and dimensions are purely exemplary as the invention may be applied in a wide variety of situations in which a single or multiple rail track is required.

We claim:

I. A rail track comprising a plurality of prestressed concrete sections each having a bottom face engaging the ground, said sections being spaced in longitudinal direction from each other and each comprising an elongated body of concrete and a plurality of post tensioned stressing tendons bonded to said body of concrete and having opposite end portions extending beyond opposite ends of the body of concrete; means in the space between said sections for connecting the end portions of said stressing tendons of one section to the end portions of the adjacent section in stressed condition; concrete means filling the spacing between adjacent sections and to thereby form a continuous common base with said sections; and a plurality of rails laid on and secured to said base.

2. A rail track support as defined in claim 1, further comprising a second concrete section situated on said common base, the lower flanges of the rails being embedded in said second concrete section; and fixing means embedded in said first and second sections for fixing said sections to each other.

3. A rail track support as defined in claim 2, wherein said fixing means comprises a spiral steel wire.

4. A rail track support as defined in claim 3, wherein said spiral wire has an axis and is embedded in said sections with its axis lying in said common base.

5. A rail track support as defined in claim 1, wherein said means for connecting the end portions comprises a W-section member in each space between adjoining sections extending transversely to the direction of said sections, said members having holes for receiving the opposite end portions of tendons from adjacent sections, and means for stressing said tendons by urging saig end portio r s towards sai W-SBQtlOl'f.

. A rail trac support as c aimed in c arm 1, wherein the stressing tendons of adjacent strips are joined end to end to form a continuous stressed reinforcement throughout the length of the rail track support.

7. A rail track support as claimed in claim 7, wherein additional unstressed reinforcing steel is provided in the said space between said sections. 

1. A rail track comprising a plurality of prestressed concrete sections each having a bottom face engaging the ground, said sections being spaced in longitudinal direction from each other and each comprising an elongated body of concrete and a plurality of post tensioned stressing tendons bonded to said body of concrete and having opposite end portions extending beyond opposite ends of the body of concrete; means in the space between said sections for connecting the end portions of said stressing tendons of one section to the end portions of the adjacent section in stressed condition; concrete means filling the spacing between adjacent sections and to thereby form a continuous common base with said sections; and a plurality of rails laid on and secured to said base.
 2. A rail track support as defined in claim 1, further comprising a second concrete section situated on said common base, the lower flanges of the rails being embedded in said second concrete section; and fixing means embedded in said first and second sections for fixing said sections to each other.
 3. A rail track support as defined in claim 2, wherein said fixing means comprises a spiral steel wire.
 4. A rail track support as defined in claim 3, wherein said spiral wire has an axis and is embedded in said sections with its axis lying in said common base.
 5. A rail track support as defined in claim 1, wherein said means for connecting the end portions comprises a W-section member in each space between adjoining sections extending transversely to the direction of said sections, said members having holes for receiving the opposite end portions of tendons from adjacent sections, and means for stressing said tendons by urging said end portions towards said W-section.
 6. A rail track support as claimed in claim 1, wherein the stressing tendons of adjacent strips are joined end to end to form a continuous stressed reinforcement throughout the length of the rail track support.
 7. A rail track support as claimed in claim 1, wherein additional unstressed reinforcing steel is provided in the said space between said sections. 